Burner control device



v. o. BEAM ETAL BURNER CONTROL DEVICE July 10, 1945.

Filed Au 19, 1942 IN VEN TORS Wily-11.11.. O. 13a.a.m John. MINA/5.50m fPatented July 10,1945

"UNITED STATES, I PATENT OFFICE BURNER CONTROL nnvron Vilynn 0. Beam-andJohn M.

asslgndrs to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn.,

olls Minn.,

Wilson, Minneapa corporation of Delaware Application August 19, 1942,Serial No. 455,330

20 Claims.

The present invention is concerned with a burner control device and moreparticularly to one utilizing the conductive properties of a burnerflame or utilizing the conductive properties of a photo-cell exposed tothe burner flame to control the operation of the burner.

In the co-pending application of Vilynn 0. Beam, Serial No. 450,613,filed July 11, 1942, there is described a control device designed topertorm a controlling operation in acco rdance with the rectifyingcharacteristics of andmpedance connected across the gap in the circuitconnections of. the control device. This control device is designed tofunction in one manner if the gap is bridged by a rectifying impedanceand in a different manner; if the gap is bridged by anonrectifyingimpedance regardless of the magnitude of the impedance. As brought outin said copending application, the impedance may take any desired formand particularly it may be the flame itself or a photo-cell responsiveto the light produced by the flame. a

An object of the present invention'is to provide a burner control deviceutilizing certain features of the control device of the aforesaid Beamapplication and in which the elements are arranged,

so as to be peculiarly adapted for the control of a burner by acontrolling switch such as a room thermostat.

'A further object of the present invention is to provide a, burnercontrol means having an elec-, tronic discharge device in which onewinding is both used to energize a relay circuit and also to control thebias on a control grid of the discharge device.

A still further object of the present invention is to provide a burnercontro1 device of the type set out in the previous object in which thebias on the grid is controlled by a condenser normally charged in onedirection by a transformer winding and in which the same transformerwinding also functions to energize a relay circuit coni trolled by aroom thermostat or other controlling switch.

Other objects of the present invention-will'be apparent from aconsideration of the accompany-- ing specification, claims and drawing,of which the single figure is a schematic view of the burner controldeviceconnected to a thermostat and to a burner to control the operationof the burner by the room thermostat and in accordance with thecondition of the burner flame. I

Referring to the specific form of the apparatus shown in the drawing,the burner control device ,of the present invention is schematicallyindisystem.

In general, the burner control device I0 is employed tocontrol theoperation of a motor 2| of an oil burner 22. Associated with this burneris an electrical ignitio means 23 of any conventional type, this igition means being employed to ignite the fuel issuing from the burner.Asis conventional practice, the nozzle of burner 22 is connected toground as indicated at 24.

Associated with the burner 22 is a flame electrode 26. This electrode isadapted to extend into the burner flame and to form one terminal all ofa gap between it and ground bridged by the burner flame when such aflame is. present. As will be pointed out later, the burner iscontrolled through the control device ll] of the present invention inaccordance with the character of the impedance across this gap.

The burner control device I0 is also controlled by a control switch suchas a-room thermostat 30. This thermostat is of a conventional typecomprising a bimetallic element 3| and a plurality of contact arms 32and 33 designed to engage with contacts 34 and 35. The contact arm 33 ismore widely spaced from contact 35 than is contact arm 32 from contact34. Upon a drop in temperature, contact arms 32 and 33 are designed tobe moved to the left. Because of this difference in spacing of contactarms 32 and 33 from their respective contacts, it will be obvious thatupon a temperature drop, arm 32 first engages its contact 34 and contactarm 33 does not engage its contact 35 temperature has occurred.

The power terminals l4 andrlj5 are connected by conductors 38 and 39 toline wires and 4| vention,

leading toany suitable source of power (not shown).- Thus, terminals andI5 are always at thesame potential as line wires 40 and 4| and allcircuits hereinafter referred to will be traced rom the power terminalsand I5.

Referring now to theburner control device 10 which forms the subjectmatter of the present inthis device generally comprises an elecuntil afurther drop in and 62 and a high voltage secondary 63.

tronic discharge device 42, a step-up, step-down transformer 44, a firstrelay 45, a second relay 46', and a safety switch 41.

The electronic discharge device 42 is of the double triode type, havinga double cathode 4.9

energized by a heating element v50. The first triode comprises cathode49, a grid 52 and an anode 53. The second triode comprises the samecathode 49, a grid 55 and an anode 56. As is usual, the various elementsare housed within an envelope 58. a

The step-up, step-down transformer 44 controls i the energization of theelectronic discharge device 42 as well as the various other electricalelements referred to. This transformer comprises a line voltage primary60, low voltage secondaries 6I The high voltage secondary 63is providedwith a center tap 64. The line voltage primary 60 is permanentlyconnected through conductors 66 and 61 to the power terminals I4 and I5.While any suitable voltage may be employed depending upon the voltage ofthe power source available and the operating characteristics of theelectronic discharge tube, the; primary winding 60 may, for example, beconnected to a 110 volt source of power and the windings 63, BI and 62may be designed to operate at voltages of 600 volts, 6 volts and 24volts, respectively.

The safety switch 4'1 may be of any suitable type, such as that shown inthe patent to Frederick S. Denison, No. 1,958,081, filed May 8, 1934.

As shown schematically in the drawing, the safety switch comprisesswitch blades H and 12, the lower switch blade 12 being pivotallymounted .and 'held in contact making engagement. with switch blades H bya bimetallic element 13. Located adjacent the bimetallic element 13 is aheater 14. Upon the bimetallic element 13 being heated by heater 14, forlonger than a prede-.- termined period of time, the upper end ofbimetallic element 13 is warped to the right so as to permit switchblade 12 to fall away from switch blade 1|. These switch blades can thenbe reengaged only by a manual operation. 4 Relay comprises a relay coil86 and three switch blades, 81, 88 and 89, designed to cooperate withfixed contacts 90, 9I and 92. The switch blades 81 to 89 are normallybiased out of engagement with the contacts and are moved into engagementtherewith upon energization of relay coil 86. As will be more apparentfrom the subsequent description, the relay 45 is controlled bythermostat 30 and is energized by the secondary winding 62.

The relay 46-comprises a winding 95 and a plurality of switch blades 96,91 and 98 designed to engage contacts 99, I00 and I02. Switch blades 96and 98 are biased into engagement with con-' tacts 99 and I02 whileswitch blade 91 is biased 60 out of engagement with contact I00. Uponenergization of relay coil 95, switch blades 96 and 98 are moved out ofengagement with their contacts and switch blade 91 is moved intoengagewindingf 95, and conductor III to the lower terminal of secondarywinding 63. Thus it "will 'be seen that during the half cycles in whichthe lower end of secondary winding 63 is positive with respect to thetap 64 and if the potential of grid 55 is sufficiently high with respectto cathode 49, a current will flow through the relay winding 95, themagnitude of this current being dependent upon the potential applied togrid 55. The condenser I04 acts to eliminate possible chattering of therelay.

The potential of grid 55 is determined to a large extent by the directcurrent potential existing across condenser H5. The A. C. voltageexisting across condenser II5 tends to be filtered.

out by a filter network including resistors I I6 and H1 and. a condenserH8. The direct current voltage across condenser H5 is determined byseveral factors. In the first place, the condenser H5 is subjected to adirect current potential resulting from its connection in-series withsecondary windings 6I and 62, grids 52 and 55, and cathode 49. In otherwords, the condenser H5 is connected in the grid circuits of bothtriodes. As will be pointed out later, the direct current potentialproduced by this grid current tends to charge the condenser H5 in such adirection as potential of grid .55 suiiiciently high to causevenergizationof relay coil 95.

Certain other factors affect the potential of grid 55 and these factorswill be explained subsequently.

OPERATION With the varicus elements in the position shown in thedrawing, the temperature to which thermostat 30 responds is above thedesired value.

Let it now be assumed that the temperature drops sufficiently to causemovement of contact blades 32 and 33 towards contacts 34 and 35. Noenergizing circuit is established until both contact blades have engagedthe contacts 34 and 35.

5 When this happens, a circuit is established through the relay coil 86as follows: from the lower terminal of secondary 62 through conductorsI25, I26 and I21, contact 99, switch blade 96, conductor I28, terminalII, conductor I29, contact 35, switch blade 33, contactblade 32, contact34, conductor I30, terminal I2, conductor I3I,- relay coil 86, conductorI32, switch blades H and 12, conductor I33, heater 14, and conductorI35. to the other terminal of secondary 62. The result of theencrgization of the relay coil 86 by reason .of the establishment of thecircuit just traced is that switch blades 81, 88 and 89 are tors I25 andI26, switch blade 81, contact 90,

conductor I31, terminal I3, conductor I38, bimetallic element 3I,contact blade 32, contact 34, conductor I30, terminal I2, conductor I3I,

relay coil'88, conductor I32, switch blades H and 12, conductorI33,,.heater 14, and conductor I35 to the other terminal oi secondary62. It will be noted that the circuit just traced is independent ofcontact blade 33 and contact 35. The result of this is that upon a risein temperaturathe circuit to relay coil 86 will not be interrupted untilboth contact blades 32 and 33 have sep arated from their contacts. Inthis way, a dif- II5. It is also to ferential intemperature is necessaryto cause deenergization oi the relay after it has been energized. Thus,chatteringoi therelay is avoided. Likewise, this circuit is independentof contact blade 99 and contact 99 of relay 46.

I conductors I40 and I41, contact I02, switch blade 98, conductor I48,terminal I1, conductor I5I, ignition means 23, conductor I49, terminall8 and conductors I50 and I45 to the other terminal I5. As a result ofthe establishment of these circuits, the oil burner motor is placed inoperation to feed fuel through the nozzle and the ignition meansisenergized to provide for ignition of this fuel. Under normalcircumstances, the issuingfuel will be ignited by the ignition means. Itis highly desirable, however, that if ignition does not occur properly,the system will be shut down so that unignited fuel will not continue toissue from the nozzle. The engagement of'relay switch blade 88 withcontact 9I results in the establishment of the following energizingcircuit to cathode heater 50: from the lower end of secondary I 62through conductor I25, switch blade 88, contact 9|,

conductor I 35, cathode heater 50, and

conductors I31 and IE back to the lower terminal of secondary Theestablishment of this circuit'results in the energization of. heater 50so as to place the discharge device 42, after the lapse of a fewseconds, into condition for operation.

The burner control device I II is designed to function to check thepresence offlame. As previously noted, the direct current potentialacross condenser I I 5 tends to determine the bias on grid 55 and hencewhether the relay coil 95 is energized or not. In the absence of a flameand under normal conditions, current flows through the following circuitincluding condenser -I I5: from the upper terminal of secondary 52through conductor I55, condenser I I5, conductor I55, resistance I51,conductor I59, grid 52, cathode 39, and conductors I08, I01, I59 andI60, secondary 5I and conductor I62 to the lower terminal of secondary52. Due to the rectifying action of the gridcathode circuit, currentflows through this circuit only when the upper terminal of secondary 52is positive. In other words, condenser II5 is connected acrosssecondaries 5I and 52 in series connected by conductors I55 and I61between the junction of resistances I I6 and H1 and the Junction ofconductors I01 and I08 leading to cathode 49. It is believed parent thatthe condenser I I8 is' connected between the grid 55 and cathode 49 at apoint intermediate the resistances I I 5 and H1, The condenser H8, hencetends to filter out any alternating current voltage components thatwould otherwise be impressed between grid 55 and cathode 49.

Due to the fact that grid 55 is connected to the lower end of condenserII5, which as previously noted is charged negatively when no flameexists, the grid 55 is at a sufliciently low potential with respect tocathode 49 that insuflicient current flows in relay coil 95 to underthese conditions, the various switches of relay 46 occupy the positionshown in the drawdo the upper half of secondary ing. It is necessary,however, 'that'this relay be energized to' prevent. the system shuttingdown. The action whereby the system is shut down will be referred tolater. For the present, it is assumed that a flame properly occurs.

When flame does occur, a new, energizing circult is established Thiscircuit extends from the upper terminal of secondary 53 throughconductor I10, resistance I12, conductors I13 and I14, resistance I15,conductor I16, terminal I9, conductor I13, flame electrode 26, throughthe flame, conductor 24 to ground, through the ground to groundconnection I19, and through conductor I55, condenser II5, conductor I55,secondary 52, conductor I52, secondary GI,

tap 64 of secondary 53. It will be noted that in the circuit justtraced, a condenser II5 is connected in series with the flame gap andthat por-- tion of secondary 63 between tap 64 and the upper end of thesecondary. The full voltage. 01'

the flame gap, however, since secondaries 62 and BI are also included inthe circuit. The voltage that is hence applied is the voltage across theupper half of secondary 63 minus the combined voltages of secondaries 5tand 52. As is indicated by the typical voltage valeus of the secondariesgiven in an earlier portion of the specification, the combined voltagevalues of secondaries GI and 62 are relatively small as compared withthat of the upper half of secondary 53. Hence,

a relatively substantial voltage is applied across with a rectifier. Theresultof this action is that is impressed across con- 7 gation of theflame.

I01, I59 and I 60 to the other terminal of the combined secondaries BIand 52, which in turn are connected to the upper terminal of condenserbe noted'that condenser H8 is the flame gap.

In the circuit. traced in the preceding paragraph the circuit was tracedfrom the upper ter minal of secondary 53 through flame electrode 25 toground and through condenser II5 in the direction opposite to which thefirst mentioned condenser charging circuit was traced. While a certainamount --of current flows through the flame in both directions, thecurrent flow through the flame in the direction traced is much greaterthan that in the opposite direction. This is due to the rectifyingproperty of the flame. It is well established that electrons tendto flowto a greater extent in the actual direction of propa- I-Ience, theconventional current flow is greater in the direction opposite thepropagation of the flame. As a result, the current flow through theflame and through the condenser II5 tends to impress across the:condenser a direct current potential which is opposite in polarity tothat impressed by the current flow through the grid circuits. The resultis that the condenser II5 no longer tends to bias the grid 55 negativeor at least does not bias'it energize the same. Thus.

through the condenser II5.

and conductors I60, I59 and I06 to 63 is not applied to 06 remainsenergized.

The engagement of switch blade 31 with con-.

suiflciently negative to ,cause deenersiz ation of relay coil 35. Thus,suflicient current flow takes place in the output circuit of the triodeincluding anode 56 and cathode 43 to cause relay coil .33 tobe'energiz'ed with thelresult that switch.

blades 33 and 33 are'moved outof engagement with contacts. 99 and I02and switch blade3'l is moved into engagement with contact I00.

The movement of switch blade 33 out of engagement with contact 33interrupts the original energizing circuit for relay coil 86. In view ofthe fact, however, that the holding circuit has been previouslyestablished by the engagement of switch blade 81 with contact, the relaycoil tact I establishes a new energizing circuit to relay coil 06 asfollows: from the upper terminal 'of, secondary 02 through conductorsI35 and I30, contact I00, switch blade 31, cond ctor I8I,

switch blades 12 and II, conductor 32, relay coil 83, conductor I3'I,terminal I2, conductor I30, contact 34, switch blade 3'2, bimetallicelement 3I, conductor I38, terminal I3, conductor I31, contact 30,switch blade 31, and conductors I23 and I25 to the lower terminal ofsecondary 02. It is to be noted that this new circuit doesnot includethe heater I4 and that the-heater I4 is effectively shunted out byconductors I30 and I8I, switch blade 31, and contact I00. The result isthat heater I4 is substantially deener gized so that bimetallic element13 is no longer heated. Because of the shunting of heater l4, switchblades II and 12 are allowed-to remain in engagement to permit thesystem to continue in operation. In other words, since the flame has Isuch systems it is customary to deenergize the ignition means as soonasflame is established.

Assuming that the flame does not go out; the system will now continue inoperation until such time as the room thermostat is completelysatisfled. In other words, it will remain in operation until both switchblades 32 and 33 have sepa-,

rated from their associated contacts 34 and' 35. When this happens, allof the circuits previously traced to relay coil 86 are interrupted withthe result that switch blade 83'separates from contact 92 to causede'energization of the oil burner; motor. At the same time, switch'blade88 separates from contact 3I to cause deenergization of the cathodeheater 50. It is no longer necessary to heat the cathode because themoment the oil burner motor is stopped so that the flame no.

longer exists in the flame gap, the charge on con denser II5 resumes avalue such as to cause rei lay coil 35 to be deenergized.

In this connection, it is to benoted that if after normal burneroperation has been established the flame is extinguished for any reason,the relay 35 is promptly deenergized so as to cause switch blade 33 toreclose contact I02 and thus reenergize the ignition means. At the sametime,

' the shunt circuit for safety switch heater I4 is broken, as describedlater. If the conditions are still proper for initiating combustion, thereenergized ignition means will relight the burner and the cyclepreviously discussed will be repeated.

11, however, the interruption of the burner flame shutdown the system atthe end of a predetermined period of time.

This is due to the fact that the deenergization of relay coil due to theinterruption of flame also caused switch blade 31 to separate fromcontact I00 to break the Presence of other conditions than flame ornormal absence of flame As discussed in the co-pending Beam application,previously referred to, this system not only is able to differentiatebetween a normal flame and the normal absence of a flame but is able todifferentiate between flame conditions and various types of impedanceconditions across the flame gap that might otherwise falsely indicatethe presence of a flame. For example, if the system operated solely inaccordance with the magnitude of the impedance acrossthe flame gap, a

short circuit condition would cause .the system 1 'to operate as thougha flame were present. This Consider-first the situation in which due tothe" accumulation of carbon or for other reasons an impedance existsacross the flame gap which is substantially the same in magnitude asthe.im-

pedance of a normal flame. Under these conditions current .flow acrossthe flame gap .and

through condenser I III will take place. However, such impedance is notrectifying so that this current flow is the same in both directions. Itis essentially nothing more than alternating cur-' rent and thepotential impressed across condenser II5 due to this current flowtherethrough has no direct current component whatsoever. Thus, thedirect current potential across condenser ,I I5 is exactly the same asthat due to the current flow through the grid circuits. As previouslypointed out, this potential causes the grid I53 to be biased to a pointwhere relay coil 351s deenergized.

When a short circuit condition exists between the flame electrode andground, it is'obvious that the impedance is again a non-rectifyingimpedance so that the direct current potential across condenser I I5tends to be the same. However, certain other factors enter into theoperation due to the decreased impedance across the flame gap. It willbe noted that as theimpedancebetween flame electrode 28 and ground.

bias the grid 55 even more creased. This tends above, the secondary coil62 anode 53 and, cathode same secondary becomes less-and less, the grid55 tends to be connected through a relatively low impedance directly tothe upper end of secondary 63. Since the anode 56 is connected to theopposite end of secondary 63, the voltage impressed across grid 55 bythis connection tends to be 180 out of phase. Were it exactly 180 out ofphase, it would negatively and hence prevent the flow of current throughrelay coil 95. However, the condenser H and the flame impedance ineffect form a phase shifting bridge, to one terminal of which the grid55 is connected. The cathode 49 is connected to the other terminal. Theresult is that the increased voltage applied to the'grid as a result ofthe decreased impedance across the flame gap tends to be shifted so thatit is no longer 180 out of phase with respect to the voltage applied to:anode 56. Were there no compensating factor, this voltage would tend tobe displaced in phase extent as to actually raise the potential of grid55. However, the effect of the triode-including anode 53 and cathode 49is present to an increasing extent as the flame gap resistance isdecreased. It is to be noted that any decrease in "flame gap resistancetends to connect grid 52 to a point closer in potential to that of anode53. Hence, the anode current of this triode is inshift in phase so as tobring thegrid voltage more nearly 180 out of phase with the potential applied to anode 56. Reference is made to the copending Beam applicationfor a fuller explanation of this action. In any event,throughcooperative action of the anode 53, the triode including anode 5Band cathode 49 remains sufliciently non-conductive as to preventenergization of relaycoil95.

Summer that in the-operation traced through an ingenious It is to benoted circuit arrangement not age to the grid circuit of the triodeincluding 49. In other words, this secondary 62 not only is employedtoenergize thethennostatically controlled relay circuit but it is alsoemployed to charge the condenser H5 negatively. Normally, it would benecessary to include two separate secondaries since the voltagessupplied are to be distinctly different porto such an to produce acorrecting I only serves to energize the relay coil 86 but also servesto apply a volttions of the circuit which normally cannot beinterconnected. Due to the ingenious circuit arrangement of the presentdevice, however, the accomplishes both functions and thereby reduces thecost of the burner control.

It will be device, which functions with a minimum of parts to instantlydetect the presence or absenceof a flame and which is capable ofdifferentiating between a normal flame condition and conditions closelysimulating those of anormal flame.

While we have disclosed the use of. a flame electrode for detecting thepresence of a flame, a photoelectric cell could readily be substitutedfor the flame gap as disclosed in the previously mentioned Beamapplication, Such a cell due to its rectifying properties, when exposedto a source of light such as a burner flame, would introduce a.rectifying effect similar to that. of the flame itself. For thisreason,: whenever expressions such as "flame'responsive means and uponthe presence of a burner flame are employed in the notedthat We haveprovided an" improved burner control 5 appended claims, itis to beunderstood that these terms are to be construed broadly enough to bereadable upon operation with either a photoelectric cell or a flame gap.In general, while we have disclosed a specific embodiment of ourinvention for purposes of illustration, it is to be understood that ourinventionis limited only by the scope of the appended claims.

We claim as our invention:

1. In a burner control means, controlling means adapted to be controlledby a main control switch and adapted to initiate steps normallyresulting second source of power connected to said biasing meansand saidcontrollingmeans for energizing both i said biasing means and saidcontrolling means.

2. In a burner control means, controlling .means adapted to becontrolled by a main control switch and adapted to initiate stepsnormally resulting in a burner operation, a grid controlled electronicdischarge device, means controlled by said device adapted to controlthe-bumer after it is in operation, a transformer having a secondarywinding adapted to supply an alternating potential, biasing meansadapted normally to bias the grid of said device so that its potentialis within one range of values, flame" responsive means associated withsaid grid and adapted to shift the potential of said grid into a secondrange of values, and connections between said secondary winding and bothsaid biasing means and said controlling means whereby both said biasingmeans and said controlling means are nergized by one secondary winding.

3. In a burner control means, a grid controlled 7 thermionic dischargedevice having a heater associated with an electron emissive surface,means controlled by said device adapted to control a burner, a.transformer having a secondary winding adapted to suppl an alternatingpotential, biasing means adapted normally to bias the grid of saiddevice 150 that its potential is within one a e of values, flameresponsive means associated with said grid and adapted to shift thepotential of said'grid into a second range oi. values upon thepresenceof a burner flame, co'ntrolne means adapted to be controlled bya main controlling switch for initiating energization' of said heater,and connections between said secondary winding and both said biasingmeans and said controlling means whereby both said biasing means andsaidcontrolling means are energized by said one secondary winding.

, 4. In a burner control means, controlling means adapted to becontrolled by a main control switch and adapted to initiate stepsnormally resulting ina burner operation, a grid controlled electronicdischarge device, means controlled by said device adapted to control theburner after it is in opera! -tion, a transformer having asecondarywinding adapted to supply an alternating potential, animpedance connected to the grid of said electronic discharge device forcontrolling the magnitude of the current in said output circuit,connections between said secondary winding and said impedance andoperative to impress across said impedance a potential'biasing said gridsufliciently negative to render said discharge device effectivelynon-conductive.v flame responsive means associated with said grid andadapted to raise the potential of said grid u on the presence of aburner flame. and connections between said secondary. windin and said'controlling means whereby the said controlling'means is ener ized bythe same secondary winding that energizes said condenser chargincircuit.

5. In a burner control means. controlling means adapted to be controlledby a main control switch and adapted to initiate steps normall resultinin a burner operation. a grid controlled electronic discharge device.means controlled by said deviceadapted to control the burner after it isin opera-.

tion, a transformer having a secondary winding adapted to supply analternating potential. 9. condenser connected to the grid of saidelectronic dischaarge device for controlling the 'magnitude flows insaid output circuit to energize. said first relay, flame responsive'means associated with said grid'and adapted upon the presence of aburner flame tochange the potential applied to said grid; to increasethe current fiow in said output circuit, and further connections betweensaid second secondary winding and said second relay to energize saidsecond relay by said secondary winding under the control of saidthermostat.

8. In aburner control device, a first relay, a grid controlledelectronic discharge device controllingthe energization, of saidrelay, asecond relay adapted to be controlled by a main controlling switch,means operative only upon energlzation of both relays, to maintaincontinued operation of a burner, a transformer having at least twosecondary windings, connections be+ tween one of said secondarywindings, said firstnamed relay and said electronic discharge deviceconstituting the output circuit of said electronic discharge device andcontrolling the energization of said first-named relay, a condenserconnected of the'current in said output circuit. connections betweensaid secondary winding and said con= denser and operative to impressacross said condenser a potential biasing said grid so that itspotential is within one range of values, flame,

responsive means associated with said grid and adapted to shift thepotential of said grid into a second ran e of values upon the presenceof a burner flame. and connections between said sec ondary winding andsaid controlling means whereby the said controlling means is energizedby the-same secondary winding that energizes said condenser chargingcircuit.

6. In a burner control device, first and secon relays, a grid controlledelectronic discharge device controlling the energization of said firstrelay, a second rela adapted to be controlled b a main control switchfor controlling a burner to control thedeliveiy of fuel thereto. meansto terminate operation of said burner within a predetermined perid oftime, means controlled by said first relay for rendering said last namedmeans inoperative in the event of energization of said first named relayby said discharge device denser to increase thecurrent flow in saidout.-

to the grid of said electronic discharge device and controlling themagnitude of the current in said output circuit, connections between asecond of said secondary windings and said condenser and, operative toimpress across said condenser a voltage such that insuiflcient currentflows in .said output circuit to energize said first-named relay, flameresponsive means associated with said condenser and adapted uponthepresence oi a' burner flame to change the energization' of saidconput circuit, and further connections between. said second secondarywinding and said second relay to energize said second relay'by. saidsecondary winding under the control of said thermostat.

9i In a burner control means, a grid controlled thermionic dischargedevice having a heater aspriorto the expiration of said predeterminedperiod of time, biasing means adapted normally tive to render saiddischarge device ineffective t0 energize said first relay, flameresponsive means associated with said grid and adapted to raise thepotential or said grid upon the presence of a burner flame. a firstsource of power operative to energize the output circuit of saiddischarge device, and a second source of power operative to, energizesaid second relay, said operation termiating means, and said'biasingmeans.

of said flrst named relay, biasing means adapted;

to be energized by a second of said secondary windings and normallyoperative to impress on the grid of said electronic discharge'device abiasing voltage such that-insufllcient current.

" to bias the grid of said device sufilciently negasociated with anelectron emissive surface, means controlled by said device adapted toccntrol a burner, a transformer having ,at least two secondary windingsadapted to supply alternating potentials, biasing means adapted normallyto bias the grid of said device so that its potential is within onerange of values, means associated with said grid and adapted to shiftthe potential. of said grid into a second range of'val'ues upon thepresence of a burnerfiame, connections between one, of said secondarywindings and said heater for energizing said heater, controlling meansadapted to be controlled by-a main'controllinghwitch for initiatingenergization of said heater. by said secondary winding,connectionsbetween a second of said secondary windings and .saidcontrollingmeans for energizing the latter,

and connections from said first and second secondary windings in seriesto said biasing means whereby said biasing means is energized by thesamev two windings as are employed to energize said heater and saidcontrolling means. I

10. Ina burner control means; controllingmeans adapted-to be controlledby a main control switch and adapted to initiate steps normallyresulting in a burner operation, a grid controlled electronic discharge"device,'means icontrolled by 1 said device adapted to control theburner after it is inoperation, a transformer having a secondary windingadapted to supply an alternating potential, biasingmeans adaptednormally to bias the' rid of said device sumciently negative to rendersaid discharge device effectively non-conductive. means including acircuit havinga gap adapted to be bridged by means exposed to a burnerflame and responsive only to the presence oi a direct current componentin the current flowing through said gap to raise the potential of saidgrid, and connections between said secondary winding and both saidbiasing means and said controlling means whereby both said biasing meansand said controlling means are energized by'said one secondary winding.

11. In a control means, a grid controlled thermionic amplifier having aheater associated with an electron emissive surface, biasing meansadapted normally to biasthe grid of said device sufliciently negative torender said amplifier effe'ctively non-conductive, means includingcircuit connections having a gap adapted to be bridged by an impedance,said last-named means being operative to raise the potential of saidgrid upon the presence of an impedance of desired characteristics insaid gap, a relay adapted to be controlled by a main controlling switchfor initiatin energization of said heater, 9, first source of powerforenergizing the output circuit of said amplifier, a second source ofpower operative to energize said heater, a third source of powereffective to energize said relay, and connections whereby said secondand third sources of power jointly energize said biasing means.

12. In combination; a transformer having windings including at least onesecondary winding; a current translating means; a space dischargeamplifier having an anode, a cathode, and a control element; meansincluding connections between said windings, said anode, said cathode,and said current translating device and operative to cause eitherenergiz'ation or effective deenergization of said device depending uponwithin which of two ranges of potential values said control element ismaintained; biasing means for normally maintaining said controlelectrode at a potential within a first of said two ranges oi values;means including a connection between said control element and a.point'on said windings, said connection including a gap adapted to bebridged by a rectifying impedance; said last named means being effective.when said gap is bridged by a rectifying impedance to maintain saidcontrol element at a potential within the action of said biasing means;a relay controlling the operation of said amplifier; and connectionsbetween said secondary winding and both said biasing means and saidrelay so that both said biasing means and said relay arejenergized bysaid one secondary winding.

anode, a cathode, and a control element; meansincluding connectionsbetween one of said secondary windings, said anodefsaid cathode, andsaid first relay and operative to causeeither energizationor eilectivedeenergization of said relay .depending upon within which of tworanges'of potential values said control element is maintained; biasingmeans for normally maintaining said control electrode at a potentialwithin a first of said two ranges of values; a connection between saidelement and a point on said one secondary winding such that theconnection tends to maintain said control element at an alternatingpotential also within said first of said two ranges of values, saidconnection including a gap adapted to be bridged by a rectifyingimpedance; means associated with said connection and" effective whensaid gap is bridged by a rectifying imped- "ance to maintain saidcontrol element at a potentialwithin the other of said two ranges ofvalues against the action of said biasing means; a second'relaycontrollingthe operation of said amplifier; and connections between asecond of said secondary windings and both said biasing means and saidsecond relay so that both said biasing means and said second relay areenergized by said second secondary winding.

15. Inc, control means, a grid controlled thermionic amplifier havingaheater associated with an electron emissive surface, a transformer hav-"other of said two ranges of values against the 13. In combination; atransformer having and said current translating device and operative tocause either energization or effective de-.

ing three secondary windings eachadapted to supply alternatingpotential, biasing means adapted normally to bias t? grid of said am,-plifier sufficiently negative to render said amplifier eifectivelynon-conductive, means including circuit connections having'a gap adapted"to be bridged by an impedance, said last-named means being operative toraise the potential of said grid upon the presence of an impedance ofdesired characteristics in said gap, controlling means adapted to becontrolled bya main controlling switch for initiating energization ofsaid heater. connections between a first of said windings and the outputcircuit of said thermionicamplifier, connections between a second ofsaid windings and said heater, connections between a third of saidwindings and said controlling means, and

energization of said device depending upon within which of two ranges ofpotential values said control element is maintained; biasing means fornormally maintaining said control electrode at a potential within afirst of said two ranges of point on said windings such that theconnection tends to maintain said control element at an al.

pedance; means associated with said connection and eflective when saidgap is bridged by 8 rectifying impedance inc-maintain said controleleconnections whereby said second and third windingsare connected inseries to energize said biasing means.

16. In a burner trically operated means for controlling the flow of fuelto said burner, a main controlling thermostat, means controlled by saidthermostat for initiating burner operation, a grid controlled electronicamplifier, means controlled by the amplifier and operative to controlthe burner after it is in operation, biasing means adapted normally tobias the grid of said amplifier so that its potential is within onerange of values, flame responsive means associated with said grid.adapted-to shift the potential ofsaid grid intoa different range ofvalues upon the presence of a burner flame, a first source of powerconnected to enercontrol system, a burner, elecsize the output circuitoi said plifier, and o single second source of power connected to saidbiasing means and to said thermostatically controlled means forenergizing both said biasing means and said thermostatically controlledmeans.

17. In a burner control system, a, burner, electricslly operated meansfor controlling the flow of fuel to said burner, ignition means forigniting the fuel supplied to said burner, a thermostat, meanscontrolled by said thermostat for initiating energization of saidignition means, a grid controlled electronic amplifier, means controlledby said amplifier operative to control said burner, biasing meansadapted normally to bias the grid of said amplifier so that itspotential is within one range of values, flame responsive meansassociated with said grid adopted to shift the potential of said gridinto a difierent range of values upon the presence of a burner flame, afirst source of power connected to energize the output circuit of saidamplifier, and asingle second source of power connected to said biasingmeans and to said thermostatically controlled means for energizing bothsaid biasing means and said thermostatically. controlled xneans.

18. In combination, on electronic amplifier having a. control electrode,a relay adapted to be controlled by seid amplifier and having a relaywinding and control elements actuated thereby adapted to control saidamplifier, a plurality of sources of alternating power, one of saidsources being connected to energize the output circuit of saidamplifier, biasing means adapted normally" to maintain said controlelectrode at a potential such that said amplifier is edectivelynon-conducting, connectionsbetween a. second or said sources of powerand both said relay winding and said biasing means for causing'saidsingle other source of power to energize both said relay winding andsaid biasing means, a. connection between said control electrode and apoint on said first named source such that the connection tends to aidsaid biasing means, said connection including a. gap adapted to bebridged by a, rectifying impedance, and means associated with saidconnection and effective when said gap is bridged by a rectifyingimpedance to maintain said grid at a different. potential such that saidamplifier is efiectively conductive,.

19. In combination, on electronic empllfier having a control electrode,a relay adapted to be conesert electrode at a. potential such that saidamplifier is efiectively non-conducting, connections between ssecond ofsaid secondary windings and both said-relay winding and said biasingmeans for we said single other source oi. power to energize both saidrelay win and said biasing mesns, a coecticn between said controlelectrode and a point on sold first named secondary ding such that theconnection tends to aid said biasing means, said connection including agap adapted to be bridged by a rectifying impedonce, and meansassociated withsaid connection and eflective when said gap is bridged bya rectifying impedance to maintain said control electrade at a difierentpotential such that said amplifier ls enfectivelyconductive.

, 20. In combination, an electronic amplifier having a controlelectrode, a relayadapted to be controlled by said amplifier and havinga relay winding and control elements actuated thereby and adapted tocontrol said amplifier, a. transformer having a plurality of secondarywindings, one of said secondary windings being connected to enersize theoutput circuit of said amplifier, biasing means adapted normally tomaintain said control electrode at a potential such that said amplifieris effectively non-conducting. connections between a second or saidsecondary windings and both said relay win and said biasing means forcausing said single other source of power to enersize both said relaywinding and said biasing means, a connection between said controlelectrode and a point on said first ed secondary winding such that theconnection tends to' aid said biasing means, said connection including asap adapted to be bridged by a. rectifying impedonce, and meansincluding a condenser associated 45 with said connection and effectivewhen said gap is bridged by a rectifying impedance to assume a chargesuch as to maintain said control electrode at a; diflerent potential atwhich said amplifier is efl'ectively conductive.

.vnmm 0. B-EAM. some M. WILSON.

